Argentina’s constitution was amended in 1994 and the position of prime minister was created. (See a previous post). While, for me, this doesn’t make Argentina semi-presidential, it is clear that the pros and cons of establishing a semi-presidentialism system were actively debated.
The process began with the creation by President Alfonsín of the Consejo para la Consolidacion de la Democracia in 1985. The process was completed with the so-called Pacto de Olivos in December 1993. The recommendations of the Consejo para la Consolidacion de la Democracia, at least as far as they concerned the prime minister, were pretty similar to the ones that were adopted in the end.
An article (in Spanish) by Carlos Nino from 1989 in favour of semi-presidentialism in Argentina is available here.
An article (in English) by Gabriel Negretto that gives information about the debate over presidentialism/semi-presidentialism (p. 14 onwards) can be found here.
In Arend Lijphart’s edited volume Parliamentary vs Presidential Government (OUP, 1992), there is a short extract from the report of the Consejo para la Consolidacion de la Democracia.
There is a nice resume (in Spanish) on the process as a whole by Alejandro M. Garro in the Revista Española de Derecho Constitucional, 1989.